Gipronikel Institute LLC, Saint Petersburg, Russia

I. V. Klimenko, Junior Researcher, e-mail: KlimenkoIV@nornik.ru
M. B. Greyver, Head of the Nickel Refining Sector

Kola MMC, Monchegorsk, Russia
A. N. Sheloputov, Senior Process Engineer at the Nickel Electrowinning Plant

The launch of nickel cathodes production by electrowinning at Kola MMC’s Nickel Electrowinning Plant was associated with significant changes in the flows and compositions of nickel solutions during scrubbing operations, such as the iron removal stage. These operational changes entailed a number of issues, such as high concentration of non-ferrous metals in the cake, poor filtration performance, unacceptably high concentration of iron in the solution after the iron removal stage as some cake particles slipped through the filters. The process of iron removal from the nickel solution, which had been previously studied on a laboratory scale, and the solutions offered at that stage regarding temperature modes, feed of precipitator in split portions, feed of the gas mixture with a higher concentration of oxidizer (oxygen), were tested on a pilot scale. In order to verify the effectiveness of the above measures and to compare the developed process with the existing one, a number of experiments was conducted that simulated the process adopted at the time. The paper describes the techniques used for the pilot tests, as well as their outcomes, and compares the two processes in terms of performance. After the pilot testing, the proven solutions were adopted in industrial practice and helped achieve the prescribed iron removal performance, improve the filtration performance, and reduce the loss of non-ferrous metals with dump cake. Particular measures are listed aimed at optimizing the iron removal performance, which were implemented based on the analysis of events that took place during the start-up period and based on the results of the pilot tests. The paper also demonstrates how the key iron removal performance indicators changed in the period from 14 January 2020 till 14 June 2021, which also includes data documented before and after the proposed measures had been implemented.

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